Disclosed herein is a sensor comprising a sensing element comprising conductive features formed on a substrate; wherein the conductive features have been formed from a palladium complex ink composition that has been deposited onto the substrate to form the deposited features and wherein the deposited features have been heated to form the conductive features on the substrate. Further disclosed is a strain gauge sensor comprising a sensing element comprising conductive features formed on a substrate; wherein the conductive features have been formed from a palladium complex ink composition that has been deposited onto the substrate to form the deposited features and wherein the deposited features have been heated to form the conductive features on the substrate; wherein the palladium complex ink composition comprises a palladium salt, an organic amine that forms a palladium complex from the palladium salt, and at least one solvent, wherein the at least one solvent has a boiling point at about the decomposition temperature of the palladium complex; wherein the conductive features conform to a two dimensional substrate surface; or wherein the conductive features conform to a three dimensional substrate surface. Still further disclosed is a method comprising disposing a palladium complex ink composition onto a substrate to form deposited features; and heating the deposited features to form conductive features on the substrate.
Strain sensors are needed in structural monitoring and force/pressure sensing. Commercially available strain gauges are typically made of metal serpentine traces patterned on plastic foils which are bonded to the structures under test. The bonding step adds additional cost, places constraints on form factor, and affects measurement sensitivity.
U.S. Pat. No. 5,184,516, which is hereby incorporated by reference herein in its entirety, describes a bonded strain gauge comprising at least a first length of planar serpentine trace; support means, affixable to a surface, for supporting said at least a first planar serpentine trace and for transmitting strain and crack forces from said surface to said at least a first planar serpentine trace; circuit means, connected to said at least a first planar serpentine trace, for measuring resistance changes in said at least a first planar serpentine trace; and protection layer means, affixed to said support means and said at least a first planar serpentine trace, for protecting said at least a first length of serpentine trace and for supporting said circuit means.
Thick film strain gauges are described, for example, in U.S. Pat. No. 5,867,808. U.S. Pat. No. 5,867,808, which is hereby incorporated by reference herein in its entirety, describes in the abstract thereof a force transducer that includes an elongated lever arm attached to a substrate having a central portion and substantially planar tab regions that project outwardly from the central portion along first and second orthogonal force-detecting axes. The substrate undergoes localized strain approximately at the junctions of the tab regions and the central portion where an external force is applied to the free end of the lever arm. A thick film strain gauge material is screen printed directly onto the substrate in at least a first location and a second location and conductive pads on the substrate are electrically coupled to the thick film strain gauge material at each location to define a first strain gauge oriented along the first force detecting axis and a second strain gauge oriented along the second force detecting axis. The lever arm can be of a compliant construction to provide propriorreceptive feedback to a user.
Currently available sensors are suitable for their intended purposes. However a need remains for improved sensors. Further, a need remains for improved strain gauge sensors that can be prepared by additive printing. Further, a need remains for improved sensors that can be ink jet printed. Further, a need remains for conformal sensors that can be ink jet printed. Further, a need remains for conformal sensors that can be ink jet printed onto two dimensional and three dimensional substrates.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.